A more experienced Brenden Aaronson ready for another bout with Atlanta United

A lot has changed in the 221 days since Brenden Aaronson stepped onto the field at Mercedes-Benz Stadium in front of 42,000 people to make his MLS debut.

The Philadelphia Union, who at the time were winless after losing two straight to open the season, have completed the best season in team history, finished third place in the Eastern Conference and won a playoff game, all with Aaronson playing a major role in the midfield. He’s also earned a call-up to the U.S. men’s national team and just this week celebrated his 19th birthday.

“It’s definitely a lot less nerve-wracking I guess you could say because we’ve already been there, done that and we’ve played this team twice,” Aaronson said earlier this week about returning to Atlanta. “I think the atmosphere was really amazing last time so I’m super excited to be going back.”

Like he did in his debut, Aaronson scored against Atlanta United in a 3-1 win over the MLS Cup holders in August for his third goal of the season. It was also his second goal of the season against veteran goalkeeper Brad Guzan. His first goal to beat Guzan led to the team’s first point of the season and inspired a poster designed by Sons of Ben Tifo Director Ryan Bross that was displayed at the game back in Chester.

To earn his first start on such a big stage back in March, against the defending champions, showed the faith head coach Jim Curtin had in his homegrown midfielder early into the campaign.

“It’s not easy for any player young or old to step on the field in Atlanta,” head coach Jim Curtin said earlier this week. “I can tell people maybe who’ve never been here, it is an atmosphere that rivals anywhere and I’m not just saying this in the country, I’m saying in the world; it gets that loud. So you can’t really prepare for it and for an 18-year-old to step on the field with the confidence he did on that day and score a goal only helps.”

That he performed so well on that stage, in an atmosphere the Medford, N.J. native said was what he imagined playing in the Champions League is like, only strengthened the belief for both coach and player.

“I think it can be the catalyst for his career and scoring a goal like that pushed him on for the rest of the season and put him now in our U.S. national team,” Curtin said. “Moments like that define professional athletes and Brenden took his chance and ran with it.”

Curtin wouldn’t say whether Aaronson would be starting again for tonight’s game during his weekly press conference on Wednesday, but he said both Aaronson and Marco Fabian would play key roles in the match.

Aaronson has started seven of the team’s last eight games — he didn’t play in San Jose — and has 26 starts and 29 appearances between the regular season and playoffs. Two of his best matches this season have come against Atlanta, which is seeking a third trophy in three months after winning the Campeones Cup and U.S. Open Cup in August.

“It will be a tough game; I’m super excited for it,” he said.